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  <div class="question_difficulty">
   难度：Easy
  </div>
  <div>
   <h1 class="question_title">
    172. Factorial Trailing Zeroes
   </h1>
   <p>
    Given an integer
    <i>
     n
    </i>
    , return the number of trailing zeroes in
    <i>
     n
    </i>
    !.
   </p>
   <p>
    <strong>
     Example 1:
    </strong>
   </p>
   <pre>
<strong>Input:</strong> 3
<strong>Output:</strong> 0
<strong>Explanation:</strong>&nbsp;3! = 6, no trailing zero.</pre>
   <p>
    <strong>
     Example 2:
    </strong>
   </p>
   <pre>
<strong>Input:</strong> 5
<strong>Output:</strong> 1
<strong>Explanation:</strong>&nbsp;5! = 120, one trailing zero.</pre>
   <p>
    <b>
     Note:
    </b>
    Your solution should be in logarithmic time complexity.
   </p>
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   <h1 class="question_title">
    172. 阶乘后的零
   </h1>
   <p>
    给定一个整数
    <em>
     n
    </em>
    ，返回
    <em>
     n
    </em>
    ! 结果尾数中零的数量。
   </p>
   <p>
    <strong>
     示例 1:
    </strong>
   </p>
   <pre><strong>输入:</strong> 3
<strong>输出:</strong> 0
<strong>解释:</strong>&nbsp;3! = 6, 尾数中没有零。</pre>
   <p>
    <strong>
     示例&nbsp;2:
    </strong>
   </p>
   <pre><strong>输入:</strong> 5
<strong>输出:</strong> 1
<strong>解释:</strong>&nbsp;5! = 120, 尾数中有 1 个零.</pre>
   <p>
    <strong>
     说明:
    </strong>
    你算法的时间复杂度应为&nbsp;
    <em>
     O
    </em>
    (log&nbsp;
    <em>
     n
    </em>
    )
    <em>
     &nbsp;
    </em>
    。
   </p>
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